1. Field of the Disclosure
The present disclosure relates generally to printers, and more particularly, to fluid ejection devices for printers.
2. Description of the Related Art
A typical fluid ejection device (heater chip) for a printer, such as an inkjet printer, includes a substrate (silicon wafer) carrying at least one fluid ejection element thereupon; a flow feature layer configured over the substrate; and a nozzle plate configured over the flow feature layer. The nozzle plate and the flow feature layer of the fluid ejection device are generally formed as thick layers of polymeric materials. The flow feature layer includes flow features (fluid chambers and fluid channels), and the nozzle plate includes a plurality of nozzles. Further, the fluid ejection device includes contact pads on both end portions thereof. Furthermore, the fluid ejection device includes fluid flow vias (through ink slots) within the substrate such that nozzles of the nozzle plate are located on both sides of the fluid flow vias. In addition, circuits for digital control and power distribution are routed longitudinally along the fluid flow vias. The circuits for digital control and power distribution are coupled with the at least one fluid ejection element to provide digital and power signals to the at least one fluid ejection element.
When fabricating a narrow fluid ejection device (e.g., a heater chip of width less than about 2 millimeters (mm) with cyan, magenta, yellow, blacK, and blacK (CMYKK) fluid flow vias) for cost saving and stationary head printing purposes, wall of a fluid flow via is needed to be reduced to a dimension (width) less than about 0.2 mm. However, such a reduction in the dimension of the fluid flow via's wall may greatly challenge longitudinal circuit routing to control and fire the nozzles. Further, in-line seamless stitching of multiple fluid ejection devices requires ultra narrow (less than about 0.1 mm) solid silicon at end portions of the fluid ejection devices. Accordingly, contact pads are needed to be situated along the length of the fluid ejection devices. Further, transverse circuit routing needs to be provided through spaces among the fluid flow vias for an appropriate and optimum utilization.
FIG. 1 depicts a top view of a partial layout of a fluid ejection device 100 (without a nozzle plate and a flow feature layer) for a 1600 dots per inch (dpi) print resolution. The fluid ejection device 100 includes a substrate 110 having a thickness ranging from about 200 micrometers (μm) to about 700 μm. The substrate 110 includes at least one trench, such as trenches 112, 114, and 116, in a bottom portion (not shown) thereof. Each trench of the trenches 112, 114, and 116 has a width ranging from about 100 μm to about 120 μm, and is configured along the length of the fluid ejection device 100. The substrate 110 further includes a plurality of fluid flow vias, such as a plurality of fluid flow vias 122, a plurality of fluid flow vias 124, and a plurality of fluid flow vias 126, arranged over the trenches 112, 114, and 116, respectively. Specifically, the fluid flow vias 122, 124, and 126 are arranged within a top portion (not shown) of the substrate 110. More specifically, the fluid flow vias 122, 124, and 126, are arranged in two rows (not numbered) over the respective trenches 112, 114, and 116, i.e., two rows of the fluid flow vias 122, 124, and 126, are laid out evenly above the respective trenches 112, 114, and 116. For the purpose of simplicity, solid space of the substrate 110 among each respective fluid flow vias of the fluid flow vias 122, 124, and 126, is not depicted and the trenches 112, 114, and 116 configured underneath are made visible in FIG. 1.
The fluid flow vias 122, 124, and 126, may be configured for fluids of specific colors. In all, the fluid ejection device 100 may include five color fluid flow vias, including the fluid flow vias 122, 124, and 126. It will be evident that the fluid flow vias 122, 124, and 126 are shown to be circular in shape. However, the fluid flow vias 122, 124, and 126 may be of any other appropriate shape, such as a rectangular shape. Further, each of the fluid flow vias 122, 124, and 126 has a depth (i.e., thickness of fluid flow via layer (not numbered)) ranging from about 30 μm to about 60 μm. The term, ‘fluid flow via layer’, as used herein above relates to the top portion of the substrate 110 that includes the fluid flow vias 122, 124, and 126, therewithin.
Nozzle pitch for the fluid ejection device 100 (1600 dpi print resolution) is about 31.8 μm from which width for fluid flow vias is deducted to obtain solid space for digital circuit and power routing. The term, ‘nozzle pitch’ for any fluid ejection device, such as the fluid ejection device 100, may be defined as an interval between centers of the recording nozzles. As depicted in FIG. 1, the restraining dimension for transverse bus routing (digital circuit and power routing) is about 31.8 μm (1″/800, i.e., 2″/1600) that defines the distance (solid space) between adjacent fluid flow vias, such as fluid flow vias 124, of a single row, as depicted by ‘D1’. Assuming the print resolution is “a” dpi, then pitch of a fluid flow via is “2″/a”, which is the restraining dimension for transverse bus routing after deduction of the width of the fluid flow via. Further, a fluid flow via of a typical fluid ejection device, such as the fluid ejection device 100, may have a width of about 5 μm and a length of about 16 μm. Accordingly, solid space among the fluid flow vias for digital circuit and power routing is about 26.8 μm (when width of a fluid flow via is deducted from the nozzle pitch/the distance ‘D1’). Furthermore, useful space is even smaller than the aforementioned value due to alignment tolerance of fluid ejection devices. Additionally, the distance (solid space), as depicted by ‘D2’, between each of the fluid flow vias, such as the fluid flow vias 124, of a first row (not numbered) and a neighboring fluid flow via of the fluid flow vias 124 of a second row (not numbered), is the determining factor for a single-pass print resolution (1600 dpi), and is about 15.9 μm (1″/1600).
The fluid ejection device 100 also includes a plurality of electrical interconnects 132 configured over the substrate 110 to communicate digital signals and power signals to fluid ejection elements (not shown) of the fluid ejection device 100 through the digital circuit and power routing.
It is further to be noted that as nozzle spatial density rises for higher print resolutions, the reduced solid space among the fluid flow vias of the fluid ejection devices greatly challenges the digital circuit and power routing, and specifically power distribution lines carrying high current.
FIG. 2 depicts a top view of a partial layout of another prior art fluid ejection device 200 (without a nozzle plate and a flow feature layer) with 1800 dpi print resolution. The fluid ejection device 200 includes a substrate 210 having a thickness ranging from about 200 μm to about 700 μm. The substrate 210 includes at least one trench, such as trenches 212, 214, and 216. Each trench of the trenches 212, 214, and 216 has a width ranging from about 100 μm to about 120 μm to sustain mechanical integrity and a low cost of the fluid ejection device 200. Further, each trench of the trenches 212, 214, and 216 is configured along the length of the fluid ejection device 200, and within a bottom portion (not shown) of the substrate 210.
The substrate 210 further includes a plurality of fluid flow vias, such as a plurality of fluid flow vias 222, a plurality of fluid flow vias 224, and a plurality of fluid flow vias 226, arranged over the trenches 212, 214, and 216, respectively, and within a top portion (not shown) of the substrate 210. The fluid flow vias 222, 224, and 226, are arranged in two rows over the respective trenches 212, 214, and 216, i.e., two rows of the fluid flow vias 222, 224, and 226 are laid out evenly above the respective trenches 212, 214, and 216. It will be evident that the fluid flow vias 222, 224, and 226 are shown to be circular in shape. However, the fluid flow vias 222, 224, and 226 may be of any other appropriate shape, such as a rectangular shape. Further, each of the fluid flow vias 222, 224, and 226 has a depth (i.e., thickness of fluid flow via layer (not numbered)) ranging from about 30 μm to about 60 μm. For the purpose of simplicity, solid space of the substrate 210 among each respective fluid flow vias of the fluid flow vias 222, 224, and 226, is not depicted, and the trenches 212, 214, and 216 configured underneath are made visible in FIG. 2.
As depicted in FIG. 2, the restraining dimension for transverse bus routing (digital circuit and power routing) is about 28.2 μm (1″/900, i.e., 2″/1800) that defines the distance (solid space) between adjacent fluid flow vias, such as fluid flow vias 224, of a single row, as depicted by ‘D3’. Further, a fluid flow via of a typical fluid ejection device, such as the fluid ejection device 200, may have a width of about 5 μm and a length of about 16 μm. Accordingly, solid space among fluid flow vias for digital circuit and power routing is about 23.2 μm (when width of a fluid is deducted from the nozzle pitch/the distance ‘D3’) that is about 3.6 μm less than that of the fluid ejection device 100. Additionally, the distance (solid space), as depicted by ‘D4’, between each of the fluid flow vias, such as the fluid flow vias 224, of a first row (not numbered) and a neighboring fluid flow via of the fluid flow vias 224 of a second row (not numbered) is the determining factor for a single-pass print resolution (1800 dpi), and is about 14.1 μm (1″/1800).
The fluid ejection device 200 also includes a plurality of electrical interconnects 232 configured over the substrate 210 to communicate digital signals and power signals to fluid ejection elements (not shown) of the fluid ejection device 200 through the digital circuit and power routing.
As observed from above, the solid space among the fluid flow vias, such as the fluid flow vias 224, is reduced when a fluid ejection device, such as the fluid ejection device 200 is required to achieve a high print resolution, such as 1800 dpi. Accordingly, the digital circuit and power routing is affected. Further, it becomes even more challenging when width of the fluid flow vias is required to be greater than 5 μm for either larger droplet volumes or thicker fluid flow via layer (i.e., greater than about 30 μm).
Accordingly, there persists a need for a fluid ejection device having a layout of fluid flow vias that provides an effective transverse bus routing for appropriate digital circuit and power distribution among the fluid flow vias of the fluid ejection device, such that the fluid ejection device is capable of achieving a high print resolution, such as a print resolution greater than or equal to about 1800 dpi.